Radiation therapy is an important tool for the treatment of cancer patients. The evolution and optimization of this multidisciplinary approach to cancer therapy has drawn upon advances in diverse areas of cellular and molecular biology and genetics. Improvements in current treatment regimens will require research-oriented clinicians and basic scientists to explore the effects of radiation on normal and neoplastic tissues and to use new insights to devise strategies for optimizing therapy. Recent advances in these areas have provided not only considerable promise to patients but also opportunities for clinicians and scientists of the future. However, continuing advancement of this field is threatened by a critical shortage of research scientists with expertise in Radiation Oncology. As a major initiative within the newly formed Department of Radiation Oncology and Molecular Radiation Sciences (RO-MRS) at the Johns Hopkins School of Medicine, a specialized Laboratory Training Program has been designed to address this need. The RO-MRS Laboratory Training Program provides young scientists with an intensive laboratory research experience that is supplemented by broad and rigorous coursework. The goal is to impart the knowledge base and skills necessary to engage in cutting edge research, thereby positioning trainees to pursue academic careers. Trainees work in modern, newly constructed laboratories that are directed by renowned investigators who are leaders in basic and translational research. These laboratories house major, funded research programs in areas that include radiation responses of cancer cells, cancer genetics and epigenetics, DNA damage signaling, chromosome maintenance and genetic instability, apoptosis, senescence, DNA repair, novel therapeutic strategies and molecular mechanisms of therapeutic sensitivity - all areas critical to understanding and optimizing radiation therapy. Each trainee works in,an area that is specific to his/her needs and interests. Two types of trainees are supported by this program: 1) Physician scientists (MD or MD/PhD) and 2) Postdoctoral research fellows (PhD or MD/PhD). These junior scientists spend at least two, and preferably three years engaged in full time research in an area of interest directly related to contemporary Radiation Oncology. This application is for the support of two trainees each year.